Automotive exhaust system and muffler therefor



June 3, 1969 R. L. PLACEK AUTOMOTIVE EXHAUST SYSTEM AND MUFFLER THEREFOR Filed Feb. 6. 1967 mm m w o a I I I I !.I m m m I I I II I -mm mm 3 Q wv Ln HI I I on mm 1 Q vm I mm J vm pm lIn I I om mm ow w.

' INVENTOR RAYMOND L. PLACEK United States Patent US. Cl. 181-54 4 Claims ABSTRACT OF THE DISCLOSURE An exhaust system for automotive vehicles having a muffler provided with an inlet connected to an exhaust pipe and an outlet connected to a tailpipe. Said mufiler has at least one sound attenuating chamber which is acoustically coupled to said inlet and outlet and which is connected to one of said exhaust and tailpipes adjacent a sound pressure point therein.

BACKGROUND OF THE INVENTION In the fabrication of automotive exhaust systems it has been the conventional practice to employ a mufiier connected at its inlet to an exhaust pipe and at its outlet to a tailpipe. Said muffler has one or more sound attenuating chambers acoustically coupled to said inlet and outlet for attenuating the noise level of the exhaust gases flowing through the muffler. As will be understood from known principles of acoustics, the exhaust and tailpipes have resonant harmonic frequencies. Each such harmonic has specifically located maximum sound pressure points along the lengths of the pipes, the locations and numbers of such points being a function of the particular harmonic. However, since these maximum pressure points are located alongthe lengths of the exhaust and tailpipes, the mufiler in a conventional exhaust system is not acoustically coupled to either the exhaust or tailpipe at these maximum sound pressure points to effect the maximum attenuation of the sound wave frequencies producing them.

Therefore, this invention relates to a muflier and exhaust system in which the muflier is provided with a plurality of sound attenuating chambers acoustically coupled to an exhaust and tailpipe and to a maximum sound pressure point in at least one of said exhaust and tailpipes.

SUMMARY OF THE INVENTION According to the preferred form of the invention, there is provided an exhaust pipe adapted to be connected at one of its ends to an exhaust gas manifold and at its opposite end to the inlet of a muffler. A tailpipe is connected at one of its ends to the outlet of the muffler and has its opposite end located at a suitable gas discharge point.

Said muflier is provided with a plurality of sound attenuating chambers acoustically coupled to its inlet and outlet for attenuating the noise level of the exhaust gases [flowing through said muffler. One of said chambers is connected by an elongated conduit to a maximum sound pressure point in said exhaust pipe, and another one of said chambers is connected by a second elongated conduit to a maximum sound pressure point in said tailpipe for attenuating the noise level of the frequency producing said pressure points.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a fragmentary isometric view of an exhaust system embodying the invention; and

FIG. 2 is an enlarged longitudinal section of the mufiier shown in FIG. 1.

DETAILED DESCRIPTION As shown in FIG. 1, an exhaust pipe 10 is adapted to be connected at one of its ends to an exhaust manifold 12 by a conventional mounting flange 14. The opposite end of said pipe is connected to the inlet nipple 15 of a mufller 16. Said mufiier is provided with an outlet nipple 17 connected to a tailpipe 18 which, in the embodiment illustrated, has its discharge end open to atmosphere.

As shown in FIG. 2, the mufiier 16 comprises an elongated shell 20 closed at one of its ends by an end cap 22 supporting the inlet nipple 15 and closed at its opposite end by an end cap 24 supporting the outlet nipple 17. A baflle plate 25 is mounted in the shell 20 adjacent end cap 22 to cooperate with said end cap to form a resonator chamber 26. In a similar manner, a baflie plate 28 is mounted within the shell adjacent end cap 24 to cooperate with said end cap to form another resonator chamber 30. A second pair of bafiie plates 31 and 32 are mounted in spaced relation to each other to form an enlarged resonator chamber 33, with plates 31 and 25 defining an end chamber 34 and plates 32 and 28 defining an end chamber 35.

A tube 37 having openings 38 formed therein is mounted in the plates 31 and 32 and is connected to the inlet nipple 15. A shell 40 is mounted on tube 37 and has portions thereof spaced from said tube whereby the openings 38 and the spaces between said tube and shell form a plurality of tuned resonators. A second tube 42 is mounted in the plates 31 and 32 and is provided with a plurality of openings 43. Still a third tube 44 is mounted in the plates 31 and 32 and is connected at one of its ends to the outlet nipple 17. As shown, tube 44 has a first set of openings 46, and the openings 46 and the openings in tube 42 cooperate with the chamber 33 to form a tuned resonator chamber. A second set of openings 48 are provided in tube 44 and cooperate with a shell 50 mounted on tube 44 and having portions thereof spaced from said tube whereby said openings 48 and the spaces between said tube and shell form additional tuned resonators.

As will be understood from Well-known principles of acoustics, the exhaust pipe 10 and tailpipe 18 each have certain harmonic characteristics. Each harmonic in each 7 of the pipes will have specifically located maximum sound pressure points along the length of the pipe, the number of such pressure points and their location being a function of the particular harmonic involved. For example, the third harmonic will have three maximum pressure points along the pipe which will occur at points spaced from either end of the pipe by distances of one-sixth, onehalf, and five-sixths of the pipe length. In general, such maximum pressure points are spaced from an end of the pipe by fractions L of the pipe length according to the formula:

2n where n is the harmonic number and m1 is every integer between and including 1 and n.

In order to attenuate the sound wave frequencies creating some of these maximum sound pressure points, a conduit 53 is mounted in end cap 22 with one of its ends opening into the chamber 26 and its opposite end connected to and opening into the exhaust pipe 10 adjacent one of the maximum sound pressure points. In a similar manner, an elongated conduit 54 is mounted in end cap 24 with one of its ends opening into chamber 30 and its opposite end connected to and opening into the tail pipe 18 adjacent one of the sound pressure points. Thus, the

conduits 53 and 54 constitute elongated resonator throats interconnecting their resonator chambers 26 and 30 to the exhaust and tailpipes. The resonators formed 'by the conduits 53 and 54 and chambers 26 and-30 are'tuned to attenuate the frequencies creating the sound pressure points to which the conduits are connected by selecting conduits with the proper lengths and cross-sectional extents and providing said chambers with the proper volumes according to standard acoustical engineering.

Changes in the speed of sound resulting from changes in temperature of the medium in which the sound waves are carried will also cause the maximum sound pressure points to be displaced along the lengths of the pipes and 18 from their theoretical location-s. Thus, in the normal operation of an automobile where the exhaust gases will range in temperature from about 200 -F. when the engine is cold to about 1700 F. when the engine is hot, the maximum sound pressure points in the pipes are subjected to substantial longitudinal displacement along the pipes. Therefore, the conduits 53 and 54 are connected to the pipes 10 and 12 at the locations where the .sound pressure points are displaced by reason of the temperatures of the exhaust gases. While the resonators formed by the conduits 53 and 54 and their respective chambers will effect maximum attenuation if said cone duits are located precisely at the maximum pressure points, they will, of course, still operate at high attenuating efliciencies if said conduits are located adjacent such pressure points. For example, it has been found that the resonators will operate at not less than 90% efficiency if the conduits are located at any point within a distance from the true maximum pressure po-in t equal to one-twentieth of the length of the sound wave producing the pressure point.

While the invention has been illustrated as having a pair of resonators connected to pressure points in the exhaust and tailpipes, it is to be understood, of course, that it may be desirable to only attenuate a pressure point in one or the other of said exhaust and tailpipes, and thus only one such resonator need be employed. It is to be further understood that the number and configuration of the other tuned resonators within the muffle-r will vary with the acoustical characteristics of the exhaust gas source and the attenuation desired.

I claim:

1. An exhaust system for automotive vehicles, comprising an exhaust pipe, a tailpipe, and a muffler having an inlet connected to said exhaust pipe and an outlet connected to said tailpipe, said muffler having a plurality of sound attenuating chambers acoustically coupled to said inlet and outlet, at least one chamber in'said rnufiler having an elongated throat connected directly to at least one of said exhaust and tailpipes at a sound wave pressure point therein, said throat and chamber being tuned to the frequency producing .said pressure point.

2. An exhaust system for automotive vehicles, comprising an exhaust pipe, a tailpipe, and a mufiler having an inlet connected to said exhaust pipe and an outlet connected to, said tailpipe, said mufller having a plurality of sound attenuating chambers acoustically coupled to said inlet and outlet, said rnuffier having a first chamber having-an elongated throat connected directly to said exhaust pipe adjacent a sound wave pressure point there in and a second chamber having an elongated throat connected directly to said tailpipe adjacent a sound wave pressure point therein.

3. A muffler, comprising an outer shell, a pair of end caps mounted on said shell closing the ends thereof, inlet and outlet nipples, a pair of gas-carrying pipes connected to said nipples, means in said shell forming at least one sound attenuating chamber therein acoustically coupled to said inletand outlet nipples, and a conduit mounted in one of said end caps and acoustically coupled to at least one chamber in said muffler, said conduit extending outwardly from said muflier for connection to one of said gas-carrying pipes at a'sound wave pressure point therein, said conduitand the chamber to which it is coupled being tuned to the frequency producing said pressure point.

4. Amuflier, comprising an outer shell, a pair of end caps mounted on said shell closing the ends thereof, inlet and outlet nipples mounted in said end caps, a pair of gas-carrying pipes connected to said nipples, means in said shell forming at least a pair of sound attenuating chambers therein acoustically coupled to said inlet and outlet nipplesQand a pair of conduits mounted in said end caps acoustically coupled to a pair of said chambers and extending outwardly from said muflier for connection to said pair of gas-carrying pipes at sound wave pressure point-s therein.

References Cited UNITED STATES PATENTS 1,331,275 2/1920 Miles 181-44 1,499,683 7/ 1924 Nashlund.

2,065,232 12/1936 MacKenzie et a1. 181-48 2,297,046 9/1942 Bourne 181-48 2,323,955 7/ 1943 Wilson 181-4-8 2,468,454 4/1949 Mason 181-48 XR 2,991,160 7/ 1961 Claussen.

3,044,571 7/1962 Spiegel 181-51 3,090,677 5/1963 Scheitlin et al. 181-45 XR 3,107,748 10/1963 Placek 181-54 XR 3,114,432 12/1963 'Ludlow et a1. .181-59 3,220,805 11/1965 Fowler et a1. 181-45 XR ROBERT S. WARD, JR,, Primary Examiner. 

